1. The Technical Field of the Invention
The present invention is directed to a cellulase composition having an elevated content of CBHII type cellulase. Said cellulase composition is obtainable from bacteria or fungi, especially from Trichoderma. The invention is also related to treatment media containing said cellulose composition as well as to methods for treating and finishing textile materials.
2. The State of the Art
Cellulase treatment of cellulose-containing textile materials during their manufacture or finishing is known per se in the art. The enzymatic treatment for finishing of cellulose-containing textile materials is called biofinishing. Biofinishing has been used to remove all kinds of impurities and individual loose fibre ends that protrude from the textile surface. The key benefits offered by biofinishing with cellulases are permanent improval of depilling, cleared surface structure by reduced fuzz, improved textile handle, such as softness, smoothness and a silkier feel, improved drapability and brighter colors of the textile and improved moisture absorbability.
Significant strength loss of the fabric as a result of cellulase treatment is a problem associated with cellulase treatment. The strength loss is caused by cellulase-induced hydrolysis of beta-1,4-glucosidic bonds of cellulose, which in turn results in partial degradation of cellulosic polymer, and further, can result in strength loss of the fabric.
In the treatment of fabrics, cellulase derived from fungi, for example from Trichoderma reesei, is generally employed, such cellulase being composed of cellobiohydrolase (CBH), endoglucanase (EG) and beta-glucosidase (BG) type components. The CBH and EG components can further be divided into CBHI and CBHII types and into several various EG types, the main types of the latter being EGI and EGII. The BG components do not react with cellulosic polymers, but further cleave the degradation products, for example cellobiose, that are formed as a result of the synergistic effect of the CBH and EG components.
A method for treating cotton fabrics, prior to dyeing and finishing, with cellulase solution in order to remove lint and loose surface fibres to impart a better appearance to the fabric is disclosed in the U.S. Pat. No. 5,232,85. The employed cellulase can be produced, for example, by Trichoderma reesei, T. koningii, Penicillium sp or Humicola insolens species. In the given examples, CYTOLASE 123-cellulase (Genencor Int.) was used with no detailed composition given in said publication. In addition to cellulase, the cellulase solution may contain buffers, surfactants, abrasion agents, and the like. After treatment, the tensile strength of the cotton woven fabric was reported to be at least 50 percent of the tensile strength of untreated fabric.
The original natural cellulase composition obtainable from the fermentation medium, which is derived directly from the microbes, for example from T. reesei fungi, is seldom suitable as such to give a desired result. The original cellulase composition may comprise about 45-80% CBHI, 10-25% CBHII, 5-15% EGI and 8-15% EGII of the total cellulase protein content. The interrelations of the CBH and EG components contained in a composition may hence be changed by various methods known to persons skilled in the art. Such methods include, for example, fractionation and genetic engineering.
The U.S. Pat. No. 5,120,463 for example discloses a detergent composition comprising a surfactant and additionally 0.002 to 10 weight percent of cellulase composed of CBHI type and EG type components with the ratio of CBHI to (EGI+EGII) being .gtoreq.10:1.
The International Patent Application WO 93/22428 discloses a method for treating cotton fabrics with fungal cellulase compositions comprising CBHI type and EG type components in a weight ratio greater than 10:1. The application mentions that the tensile strength of treated fabric is at least about 50 percent of the tensile strength of untreated fabric. No test results, however, are given.
In the International Patent Publication WO 94/23113 a method for treating cotton-containing and non-cotton cellulosic fabrics during manufacture to reduce lint generation is also described. The cellulase compositions contains all EG type components to all CBH type components in a ratio of greater than 5:1.
In the International Patent Publication WO 92/06221 cotton-containing fabrics treated with a cellulase solution essentially free from CBHI type cellulase components are said to have a decreased strength loss as compared to fabrics treated with cellulase solution containing a complete cellulase composition.
It is also known in the art that the activity of the cellulase composition depends on the acidity of the environment in which the treatment is carried out. Most generally, the activity is at its highest at slightly acid pHs, even though compositions functioning in a neutral environment may also be employed, and even such cellulase compositions are known to act in alkaline conditions. However, compositions used in a neutral or alkaline environment have a prolonged reaction time, i.e. the compositions are acting slower. Because time means money, time consuming treatments are not only less time-effective but also less cost-effective. Alternatively, more equipment is required to treat the same amount of fabrics in the same time. This is also expensive and requires additional space and facilities. Naturally, buffers known to persons skilled in the art are used to adjust the acidity of cellulase treatment media, but it does not solve all the problems.
The problem of obtaining improved color retention/restoration properties as well as improved softening and feel and visual appearance properties to cotton fabrics has been discussed in several patents and patent applications.
In the U.S. Pat. No. 5,090,474 for example a detergent composition containing substantially pure EGIII is described. The composition contains no more than 5 weight percent of CBHI type components.
The International Patent Publication WO 92/06210 describes a cellulase composition, which is enriched with unspecified endoglucanase type components. The ratio of EG type components to all CBHI type components is greater than 5:1. The composition is said to impart improved softening properties as well as retention/restoration properties to the detergent composition when used in acidic, neutral or alkaline washing media.
U.S. Pat. No. 5,246,853 discloses an improved method for treating cotton-containing fabrics with fungal cellulase compositions which are essentially free from CBH I type cellulase components, but contains at least 10% of unspecified EG type components based on the total weight of proteins in the cellulase solution.
In the International Patent Publication WO 92/06165 a cellulase composition is disclosed which composition contains 0.01-5 weight percent cellulase components. The compositions contains one or more unspecified EG type components and of all cellulase components less than 5 weight percent is of CBH I type components.
The International Patent Publication WO 95/25840 describes a cellulase composition, which is essentially free from CBH I type cellulase components and has a weight ratio of all EG-type components to all CBH I type components of greater than 5:1. Said International Patent Application corresponds to U.S. Pat. No. 5,525,507, which discloses a composition useful for treating non-cotton material. The composition is essentially free of all CBHI type cellulase components and the improved properties are achieved by modifying the naturally complete fungal cellulase composition by adding at least 10 percent of unspecified endoglucanase components.
The International Patent Publication WO 92/17572 describes a cellulase composition, which is essentially free from CBH I type cellulase components and comprises at least about 20 weight percent of unspecified EG type components.
The International Patent Publication WO 92/17574 describes a cellulase composition, which comprises one or more unspecified EG component and one more CBHI component and the ratio of all EG to all CBHI components is greater than 5:1.
In view of the above, the primary problem of using cellulase compositions in the treatment and finishing of cellulose-containing textile materials has not only been the strength loss of the fabric as a result of the cellulase treatment but also the fact that even if the proportions of CBH and EG type components have been changed in the most subtle ways as suggested in the prior art patents and patent applications no significant change in the biofinishing properties has been achieved. It seems as if the different ratios of CBH and EG type components are varied more or less randomly and the results, such as removal of impurities and individual loose fibre ends that protrude from the textile surface are as randomly obtainable. The key benefits claimed by the patents and patent application using different ratios of EG and CBH type components in biofinishing, i.e. permanent improval of depilling, cleared surface structure by reduced fuzz, improved textile handle, such as softness, smoothness and a silkier feel, improved drapability and brighter colors of the textile and improved capability of absorbing moisture seems to be essentially unchanged even if the ratios of EG and CBH vary.
Furthermore, the removal of certain components and addition of other components to the natural complete fungal cellulase composition is not necessarily sufficiently cost-effective.
We have now surprisingly found that it is not the different ratios of CBH components others than CBHII and EG components that gives the improved properties in manufacturing and finishing of textiles, but an increased level of CBHII is responsible for the improvement. The same or even better results in manufacturing and finishing are obtained as soon as even small amounts of CBHII type component(s) are added to the natural complete cellulase composition background. This improvement is totally independent of the ratios of CBH and EG disclosed in prior art.
Thus, the objective of the present invention is to provide an improved cellulase composition for treating cellulose-containing textile materials that gives a smooth feel, improved appearance and softness and improved depilling properties to the textile.
In particular, the objective of the present invention is to provide an improved cellulase composition for treating cellulose-containing textile materials that would not result in significant strength loss of the textile as a result of the treatment.
Further, the objective of the present invention is to provide an improved treatment medium for cellulose-containing textile materials that may comprise, in addition to the cellulase composition of this invention, for example, surfactants, polymers, buffers, bulk agents, preservatives, stabilizers and/or abrasion agents.
The objective of the present invention is to provide compositions with a decreased reaction time, i.e. compositions which act more rapidly. This means more time- and cost-effective treatment procedures and savings in equipment as well as treatment facilities.
The objective of the present invention is additionally to provide an improved method for treating cellulose-containing textile materials so as to preserve the strength properties, as well as to obtain an improved appearance and smooth feel of the textile.
The described objectives of the present invention have been achieved by employing a cellulase composition invention which comprises elevated amounts of CBHII type cellulase as compared to the natural complete cellulase compositions as well as those cellulase compositions known from prior art.
The improved cellulase composition of the present invention is obtainable from a cellulase solution produced by cultivating fungi or bacteria and collecting the spent essentially cell-free fermentation broth or medium containing the naturally occurring complete background cellulase components such as CBH and EG components, but above all an elevated content of CBHII components as compared to the natural complete cellulase compositions and the prior art cellulase compositions with different CBH and EG ratios. The elevated content of CBHII should be such that the desired effects are achieved. The CBHII type cellulase being the component which is essential for obtaining the objectives and benefits of the present invention.